The party would scrap the education watchdog and shift its main functions to the Audit Commission, which would inspect schools far less frequently.
Phil Willis, education spokesman, asked the Liberal Democrats' spring conference in Harrogate: "Just how many times can our students be tested, our schools and colleges inspected and league tables produced before it has a negative effect on learning?"
The former headteacher said the party would follow the Tomlinson proposals for 14-19 education more closely than the Government.
He said the Lib Dems would not scrap the content of A-levels and GCSEs but incorporate them within an over-arching diploma.
The Government rejected this proposal from the working party led by Sir Mike Tomlinson, choosing instead to create a separate diploma for vocational study.
Last week a TES poll of teachers carried out by FDS International found that backing for the Lib Dems had increased from 18 to 20 per cent since the 2001 election.
Paul Keogh, head of languages at King James's school in Knaresborough, north Yorkshire, spent an afternoon in Harrogate with Mr Willis and Charles Kennedy, the party's leader.
The 2003 secondary teacher of the year said he remained a floating voter although he had been impressed by the Lib Dems' education policies.
"I would have liked it if they had explained more about how the Audit Commission would replace Ofsted," he said.
"Ofsted causes a massive amount of stress but it has had a good effect on lots of schools."
A Labour spokesman said there was no point debating the scrapping of Ofsted because the Liberal Democrats "won't get a chance to do it".